Co-op/Shared-Inventory

Shared-Inventory is a format that uses lua (via specialized emulators) and IRC to communicate between multiple players. Various aspects of the game, initially limited to unique inventory items, are shared to both players as either player collects the items. Some implementations of this code extend to also include things like synchronized currency and health levels. Some implementations also support persistent item location status, such as treasure chests being opened for both players once it's opened by any player.

ALttPR

The project started being developed by Andi McClure with help from some of the ALttPR development team. Her instructions and source code are available online. Her version supports several games including NES Zelda, SNES Zelda & SNES Metroid.

Her project has been forked a couple of times with the most popular and extended version by FirenX.

SMALttPR

User "txcrnr" has been working on a fork of Andi & FirenX' code to support SMALttPR. Currently, no official release has been made but you can search the SMALttPR Discord's #development channel for some files that have been uploaded during the development progress of the implementation of this game.